If some HW is on HCL, it does not mean all its features are supported (sadly but true, I learned it hard way too). Very probably the raid-controller on board of your supermicro-mobo is of software/fake/bios-type (which generally is not supported by ESXi). That's why you see disk, not array...
There is not much you can do with it. Either buy add-on true raid-controller, or use individual disks attached to on-board sata/sas-ports (you can passthrough them to VM and ceate sw-raid there)...